Unlike Outlook, Gmail does not have an "undo text" button. But it does have a keyboard "undo text" short-cut. Just hit Ctrl-z, and your last text entry will be deleted. You can keep hitting Ctrl-z and it will keep deleting each next-last text entry. And keep going and it will bring back deleted text. Undo text is not the only keyboard short-cut in Gmail. In fact, there are a bunch of them, many of which are real time savers or otherwise truly useful. To see a list of all such shortcuts, open Gmail and type "?" (without the quote marks), and schzam, you'll see em all.